1. Field of the Invention
The present invention relates generally to a viscous fluid drive device. In particular, the present invention is concerned with an airflow ring for a cover of a viscous fluid clutch.
2. Description of the Related Art
A viscous fluid coupling for controlling the speed of an engine cooling fan is well-known. Generally, the coupling includes a rotatable housing defining an axis of rotation. A cover is attached to the housing to form a closed interior volume divided by a plate into a working chamber and a fluid reservoir. A driven clutch plate is disposed in the working chamber and is rotatable relative to the housing. A shear zone is formed between the clutch plate and the housing. When fluid from the reservoir is introduced to the shear zone, fluid shear transmits torque from the clutch plate to the housing, thereby rotating the housing and an attached fan to provide a flow of cooling air into the engine compartment.
Fluid friction and shear in the shear zone result in high temperatures and heat build-up inside the coupling. Persons skilled in the art are well aware of the adverse effects such heat can have on a clutch and its viscous fluid. The use of fins on the outer surfaces of the housing and the cover are widely used to dissipate this heat.
The art continues to seek improvements. It is desirable to provide efficient transfer of heat from a shear zone of a viscous fluid clutch, thereby improving the operation and life of the device.